نتایج جستجو برای: gamma ray spectrometery
تعداد نتایج: 405869 فیلتر نتایج به سال:
The energy spectra of TeV gamma-rays from blazars, after being corrected for intergalatic absorption in the Extragalactic Background Light (EBL), appear unusually hard, a fact that poses challenges to the conventional models of particle acceleration in TeV blazars and/or to the EBL models. In this paper we show that the internal absorption of gamma-rays caused by interactions with dense narrow-...
If gamma ray bursts are highly collimated, radiating into only a small fraction of the sky, the energy requirements of each event may be reduced by several (∼ 4–6) orders of magnitude, and the event rate increased correspondingly. Extreme conditions in gamma ray bursters lead to highly relativistic motions (bulk Lorentz factors Γ ∼> 100). This results in strong forward beaming of the emitted ra...
Gamma-ray bursters emit a small fraction of their flux in X rays, and because X-ray detectors are often very sensitive they may probe the gamma-ray burst universe more deeply than the current best gamma-ray instruments. On the reasonable assumptions that spectra of bursts observed by BATSE may be used to predict the X-ray fluxes of gamma-ray bursts, and that any corona of bursts around M31 is s...
We assume that internal shocks of gamma-ray bursts (GRBs) consist of multiple sub-jets with a collimation half-angle of about several times gamma-1i, where gammai is the Lorentz factor of each sub-jet. If by chance a sub-jet is first emitted off-axis from the line of sight, the observed peak energy can be in the X-ray region. Next, if by chance a subsequent sub-jet is emitted along the line of ...
We report the detection of gamma-ray emissions above 200 megaelectron volts at a significance level of 17sigma from the globular cluster 47 Tucanae, using data obtained with the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope. Globular clusters are expected to emit gamma rays because of the large populations of millisecond pulsars that they contain. The spectral shape of 47 Tuc...
Although gamma ray showers are muon-poor, they still produce a number of muons suucient to make the sources observed by GeV and TeV telescopes observable also in muons. For sources with hard gamma ray spectra there is a relativèenhancement' of muons from gamma ray primaries as compared to that from nucleon primaries. All shower gamma rays above the photo-production threshold contribute to the n...
The SPI anticoincidence shield consists of 91 BGO crystals and is operated as a nearly omnidirectional gamma-ray burst detector above 75 keV. Since the start of the mission 269 gamma-ray burst candidates have been detected. 110 bursts have been confirmed with the instruments included in the 3rd Interplanetary Network. Here we present a preliminary statistical analysis of the SPI-ACS sample of g...
Some of the very high energy (VHE) gamma-ray sources detected with the modern generation of Cherenkov telescopes have been identified with previously known X-ray binary systems. These detections demonstrate the richness of non-thermal phenomena in compact galactic objects containing relativistic outflows or winds produced near black holes and neutron stars. Recently, the well-known microquasar ...
Although gamma ray showers are muon-poor, they still produce a number of muons sufficient to make the sources observed by GeV and TeV telescopes observable also in muons. For sources with hard gamma ray spectra there is a relative ‘enhancement’ of muons from gamma ray primaries as compared to that from nucleon primaries. All shower gamma rays above the photoproduction threshold contribute to th...
The EGRET telescope aboard NASAs Compton GRO has repeatedly detected 3EG J1835+5918, a bright and steady source of high-energy gamma-ray emission which has not yet been identified. The absence of any likely counterpart for a bright gamma-ray source located 25 • off the Galactic plane initiated several attempts of deep observations at other wavelengths. We report on counterparts in X-rays on a b...
نمودار تعداد نتایج جستجو در هر سال
با کلیک روی نمودار نتایج را به سال انتشار فیلتر کنید